In this research, a ternary composite of biochar – nickel ferrite – silver phosphate has been characterized and employed for methylene blue photodegradation and mercury adsorption. Response surface methodology was adopted to optimize effective parameters on removal. It was found that maximum dye degradation and mercury adsorption was obtained at pH of 7 with dosage of 26 mg and 90 min reaction time. Moreover, the composite of biochar/NiFe2O4 /Ag3PO4 with the ratio of 70:20:10 able to remove 94 % of dye and 98.5 % of mercury at the initial concentration of 10 mg L-1. It was found that the rate of methylene blue degradation increase with increasing the temperature as it was destroyed at a temperature of 45 degrees C within 1 h. Kinetic and isotherm studies for the adsorption experiments showed that mercury adsorption followed the pseudo – second order kinetic model and Langmuir adsorption isotherm. Moreover, thermodynamic study indicated that the adsorption process is spontaneous with an endothermic path. With a good maximum adsorption capacity of 241 mg g(-1) and four cycle reusability, the prepared composite is a suitable candidate to simultaneously mitigate the side effect of dye and heavy metal in aqueous media.